This invention is particularly related to the preparation, without a phase transfer catalyst, of a polyarylene polyether ("PAPE") oligomer which is crosslinkable through its terminal vinyl groups, preferably thermally, and when crosslinked is capable of withstanding thermal degradation at a temperature in the range from above 150.degree. C. to about 200.degree. C.
This invention is more particularly related to difunctional polymers of dihydroxybenzene, dihydroxynaphthalene, and diphenols, all referred to herein as dihydric phenols ("DHP"), and the corresponding sulfur (thio) compounds referred to as dihydric thiophenols ("DHTP"), which polymers have a Mn (number average mol wt) less than about 10,000, hence termed oligomers. One or the other DHP and DHTP, or both, are referred to herein as "DH(T)P" for brevity. Such oligomers are defined herein as polymers containing from 2 to about 100 repeating units each having the formula --DH(T)P-R.sup.s --, where R.sup.s represents the residue of a compound which provides a reactive linking group. These oligomers contain at least three phenyl or thiophenyl rings which may have inert substituents, each ring linked to another through an O, Si, C or S atom. Such DHP and DHTP oligomers, also, poly[DH(T)P], or [DH(T)P].sub.n, are terminated at each end (hence "diterminated") with a phenol ("Ph") or thiophenol ("TPh") group respectively, which group may also have inert substituents. For brevity, "di-(T)Ph-terminated" refers herein to either or both oligomers which are Ph- and TPh-terminated respectively.
These oligomers are macromonomers ("macromers" for brevity) which are disclosed in copending Ser. No. 586,678 filed Mar. 6, 1984, issued Aug. 20, 1985 as U.S. Pat. No. 4,536,360 the disclosure of which is incorporated by reference thereto as if fully set forth herein.
A wide variety of macromers are known with one polymerizable vinyl head group, each of which macromers may be tailored in Mn and structural configuration to provide polymers with a wide spectrum of physical properties. Typical of such macromers are those with styryl and acrylate head groups disclosed by Kennedy, J. P. et al in I.U.P.A.C. Intl. Symp. on Macromolecules, Florence, Preprints, p 162 (1980); Polym. Prepr. Am. Chem. Soc. Div. Polym.Chem., 23, No. 2, 99 (1982); Polym. Bull., 6,] 35 (198]); inter alia.
Macromers have also been synthesized by Tsuruta by a polyaddition reaction of divinyl compounds (Makromol. Chem. 183 29-45, 1981), and by Hudecek by transformation of reactive polymer end groups (Polym. Bull. 3 143, 1980).
A thermoset product, disclosed in U.S. Pat. No. 4,116,936 to E. C. Steiner, may be a crosslinked homopolymer of bisphenol A(BPA) with styryl chain ends, or the epoxy (BPA-diglycidyl ether) copolymer, also with styryl chain ends. Though Steiner's epoxy and applicants' PAPE each have styryl chain ends, the main chains are similar only in that each has a BPA repeating unit. The polymers belong to different classes and have different properties. As is well known, BPA is also a repeating unit in polycarbonates, phenolformaldehyde resins, and in numerous other polymers none of which is a polyether. Steiner's process used acetone, methanol and benzene as solvents because he was unconcerned with removing water. Moreover, his polymers were not susceptible to the partitioning of the solvents into the polymers when they are to be recovered, which is what occurs with such solvents when our PAPE end-capped oligomers are to be recovered.
Poly(phenylene oxide) ("PPO" for brevity) may be difunctionalized by esterification as is disclosed in "Reactions of Poly(phenylene Oxide)s with Quinones. I. The Quinone-Coupling Reaction Between Low Molecular Weight Poly(2,6-Dimethyl-1,4-phenylene oxide) and 3,3',5,5'-tetramethyl-4,4'-Diphenoquinone", by Dwain M. White, Jour. of Polym. Sci., Polym. Chem. Ed., Vol 19, 1367-1383 (1981). Other difunctionalized PPO oligomers are disclosed in U.S. Pat. No. 3,663,625 to Neville, R. G. None of the prior art syntheses was concerned with reaction of alkali metal salts ("bisphenolates") of at least one of the R.sup.s -linked DH(T)P oligomers formed as described, which salts are essentially insoluble at room temperature, or only soluble in the aforementioned solvents at elevated temperatures in the range from about 70.degree. C. to about 150.degree. C. at ambient pressure, yet may be either esterified or etherified essentially quantitatively. As defined herein, Ph-terminated polyphenylene ("PP") is an oligomer of a dihydric phenol (DHP), namely 1,4-dihydroxybenzene or hydroquinone ("HQ") which may be inert substituents, in which oligomer the backbone includes at least three phenyl rings, one connected to another through an ether O atom; or, PPO oligomers which are R.sup.s -linked.
In all the foregoing prior art teachings, the macromer was produced in an organic liquid phase in which the reactants were relatively easily soluble. The bisphenolates used in the preparation of the PAPE oligomers of this invention are only difficultly soluble even in agressive solvents such as glymes, dimethyl sulfoxide ("DMSO"), and dimethylformamide ("DMF"). Because of this solubility problem, Ser. No. 586,678 disclosed a process in which a major molar amount of a phase transfer catalyst was used in aqueous alkaline conditions to form the bisphenolate of the BPA, then form the BPA-DPS oligomer, finally provide it with terminal vinyl groups at the ends of its chains. The problem of making the precursor dialkali metal salt of the BPA is exacerbated because the reaction proceeds satisfactorily only under substantially anhydrous conditions, that is, where less than 10 mole% water, and preferably less than 3 mole% water is present, and the water formed during the formation of the bisphenolate must be removed while the reaction is in progress, or the precipitated salt is subject to hydrolysis.
It is known that polymers of BPA DPS are prepared in a DMSO solution as disclosed in U.S. Pat. No. 4,108,837 to Johnson et al. But the BPA-DPS oligomer we made according to the Johnson et al process could only be partially end-capped with VB end groups. When this oligomer was fully cured its T.sub.g was below 150.degree. C. We eventually traced this low T.sub.g to be the result of small quantities of degradation products of DMSO. When this was recognized, it was decided to circumvent the problem of degradation by carrying out the distillation under vacuum. This proved to be crucial to provide substantially quantitatively VB end-capped oligomers which cured to a T.sub.g above 150.degree. C. Most of all, it must be recognized that, having produced the BPA-DPS bisphenolate in DMSO solution without the formation of deleterious degradation products, there was no indication that the reaction of ClMS would go to completion. End-capping essentially all the chains is crucial to provide the high T.sub.g sought. Remnant OH-terminated chains cannot be separated from the VB-terminated chains and depress the T.sub.g below 150.degree. C. Comparable depression of T.sub.g will be expected in other difunctionalized PAPEs.
We know of no instance where a sodium or potassium salt or other bisphenolate of a di-Na or K salt of a DH(T)P (e.g. BPA) has been prepared which is substantially insoluble in commonly available organic solvents at room temperature, yet has been used to provide a salt solution essentially free of degradation products of the solvent. Nor do we know of any instance where the salt solution is used to obtain substantially complete conversion of a PAPE oligomer such as BPA-DPS to its bisphenolate which, in turn, has essentially all its chains end-capped, all reactions being carried out without a phase transfer catalyst.
The process of our invention provides for such reactions with DH(T)Ps, and also OH-terminated oligomers of a large variety of polyDH(T)P linked through a number of different R.sup.s. The foregoing process requirements uniquely characterize the formation of the difunctionalized PAPEs of this invention, and the ability to meet these requirements permits the commercialization of these PAPEs.
Among these PAPE oligomers are (a) aromatic polyether and polythioether sulfones (all referred to as "APS" for brevity) in which the R.sup.s is a diphenyl sulfone (DPS) residue of a dihalophenyl sulfone (DHPS) linking group; (b) PPO oligomers linked with a diphenoquinone linking group, as disclosed in White, supra; and (c) aromatic polyethers and thioethers in which the R.sup.s is not a sulfone. When the DHP is bisphenol A, and the R.sup.s is DPS, the repeating unit is bisphenol A sulfone ("BPAS"); when the DHTP is bisthiophenol A, the repeating unit is bisthiophenol A sulfone ("BTPAS"), both of which sulfones are together referred to herein as `bis(thio)phenol A sulfones`, and for brevity, "B(T)PAS". As a result, salts of a wide spectrum of DH(T)P oligomers with terminal OH or SH groups may be esterified or etherified to contain terminal reactive vinyl, and more specifically VB groups, which VB-containing oligomers may then be thermally polymerized rapidly to yield solvent-resistant materials.
The difunctionalized DH(T)P oligomers are excellent molding resins which upon crosslinking are thermally stable while maintaining strength at about 200.degree. C. They may also be used as an intermediate for the synthesis of other compounds. For example, the di(styrenated) oligomer may subsequently be converted to an .alpha.,.omega.-di(ethynylbenzyl) PAPE which has terminal triple bonds known to be desirable for the development of thermally curable matrix resins for lightweight composite materials, without the evolution of volatile by-products. (See P. M. Hergenrother, J. Polym. Sci., Polym. Chem. Ed., 20, 3131 (1982).